Submission #1053482

#	Time	Username	Problem	Language	Result	Execution time	Memory
1053482		Unforgettablepl	Simurgh (IOI17_simurgh)	C++17	30 / 100	843 ms	1628 KiB

simurgh

#pragma GCC optimize("Ofast")
#include "simurgh.h"
#include <bits/stdc++.h>
using namespace std;

vector<int> find_roads(int n, vector<int> u, vector<int> v){
	int m = u.size();
	set<int> graph;
	vector<set<pair<int,int>>> adj(n);
	vector<bool> confirmed(m);
	function<bool(int,int,int)> finder = [&](int x,int p,int tar) {
		if(x==tar)return true;
		for(auto[v,idx]:adj[x])if(v!=p)if(finder(v,x,tar))return true;
		return false;
	};
	int base;
	auto differential = [&](int x){
		stack<int> edges;
		function<bool(int,int)> dfs = [&](int xx,int p) {
			if(xx==v[x])return true;
			for(auto[v,idx]:adj[xx])if(v!=p){
				edges.emplace(idx);
				if(dfs(v,xx))return true;
				edges.pop();
			}
			return false;
		};
		dfs(u[x],-1);
		assert(!edges.empty());
		vector<int> finaledges;
		while(!edges.empty()) {
			finaledges.emplace_back(edges.top());
			edges.pop();
		}
		vector<int> sameas;
		bool included = false;
		for(int&i:finaledges) {
			if(confirmed[i])continue;
			graph.erase(i);
			graph.insert(x);
			auto diff = count_common_roads(vector(graph.begin(),graph.end()));
			graph.erase(x);
			graph.insert(i);
			if(diff==base) {
				sameas.emplace_back(i);
				continue;
			}
			if(diff>base) {
				base = diff;
				included=true;
				graph.erase(i);
				adj[u[i]].erase({v[i],i});
				adj[v[i]].erase({u[i],i});
			}
			break;
		}
		if(included) {
			graph.insert(x);
			adj[u[x]].emplace(v[x],x);
			adj[v[x]].emplace(u[x],x);
			confirmed[x]=true;
			for(int&i:sameas)confirmed[i]=true;
		} else {
			for(int&i:sameas) {
				graph.erase(i);
				adj[u[i]].erase({v[i],i});
				adj[v[i]].erase({u[i],i});
			}
		}
	};
	vector<bool> visited(m);
	for(int i=0;i<m;i++) {
		if(graph.size()!=n-1) {
			for(int j=i;j<m;j++) {
				if(visited[j])continue;
				if(finder(u[j],-1,v[j])==false) {
					visited[j]=true;
					graph.insert(j);
					adj[u[j]].emplace(v[j],j);
					adj[v[j]].emplace(u[j],j);
					if(graph.size()==n-1)break;
				}
			}
			base = count_common_roads(vector(graph.begin(),graph.end()));
		}
		if(visited[i])continue;
		differential(i);
	}
	return vector(graph.begin(), graph.end());
}

Compilation message (stderr)

simurgh.cpp: In function 'std::vector<int> find_roads(int, std::vector<int>, std::vector<int>)':
simurgh.cpp:73:18: warning: comparison of integer expressions of different signedness: 'std::set<int>::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
   73 |   if(graph.size()!=n-1) {
      |      ~~~~~~~~~~~~^~~~~
simurgh.cpp:81:21: warning: comparison of integer expressions of different signedness: 'std::set<int>::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
   81 |      if(graph.size()==n-1)break;
      |         ~~~~~~~~~~~~^~~~~
simurgh.cpp:48:4: warning: 'base' may be used uninitialized in this function [-Wmaybe-uninitialized]
   48 |    if(diff>base) {
      |    ^~

• Subtask 1: 13 / 13
• Subtask 2: 17 / 17
• Subtask 3: 0 / 21
• Subtask 4: 0 / 19
• Subtask 5: 0 / 30